Thalamic relay neurons in the ventral division of the medial geniculate nucleus (MGv) provide the principal ascending input into the primary auditory cortex (AI). Neurons in AI preferentially process and respond to specific aspects of their thalamic input (Creutzfeldt et al., 1980; Miller et al., 2001; Miller et al, 2002). The goal of this project is to investigate the processes by which thalamic signals are transformed by cortical neurons. Using a brain slice preparation that contains AI, MGv, and the connecting fiber tracts, thalamorecipient cells will be categorized according to their laminar distribution, cellular morphology, intrinsic membrane properties, and the short-term dynamics of their synapses. This project has two components. First, thalamorecipient cells in auditory cortex have not been systematically characterized. We will identify and classify these cells. Second, the differences in the temporal response properties between thalamic and cortical neurons could be the result of network or cellular properties. We will investigate the role of synaptic and intrinsic membrane properties in the determining the selectivity of cortical responses to thalamic input. Our hypothesis is that distinct neuronal populations with common cellular properties will process specific temporal aspects of thalamic input.